The U.S. intelligence community has concluded that a video of an American journalist's, and former UCF student's, beheading is genuine, and President Obama vowed Wednesday to bring Steven Sotloff's killers to justice.

Obama, speaking in Estonia where he is meeting with Baltic state leaders ahead of a NATO summit in Wales, called the Sotloff's killing a "horrific act of violence."

The president said Sotloff's killers would be found and that his death would only serve to unite Americans.

"Our reach is long and justice will be served," Obama said.

Sotloff, 31, had appeared in a video released by the Islamic State last month that showed the beheading of another American journalist, James Foley. The group had threatened to kill Sotloff next. The video of Sotloff's death, entitled "A Second Message to America," was released Tuesday.

Sotloff, kneeling next to an IS member, says in the video that he is "paying the price" with his life for U.S. intervention in Iraq.

"You've spent billions of U.S. taxpayers' dollars and we've lost thousands of our troops in our previous fighting against the Islamic State," Sotfloff says. "So where is the people's interest in reigniting this war?"

"I'm back, Obama, and I'm back because of your arrogant foreign policy towards the Islamic State," the man says. He then takes a knife to the throat of Sotloff.

"The U.S. Intelligence Community has analyzed the recently released video showing U.S. citizen Steven Sotloff and has reached the judgment that it is authentic," NSC Spokesperson Caitlin Hayden said in a brief statement Wednesday. "We will continue to provide updates as they are available."

The British government said separately Wednesday that it made an unsuccessful attempt to rescue a British man — David Cawthorne Haines — being held by the Islamic State. Sotloff's killers have threatened to kill Haines if the U.S. and other western countries continue to combat IS efforts to carve an Islamic caliphate across a swath of Syria and Iraq.

"The U.S. Intelligence Community has analyzed the recently released video showing U.S. citizen Steven Sotloff and has reached the judgment that it is authentic. We will continue to provide updates as they are available," National Security Council Spokesperson Caitlin Hayden said early Wednesday, in emailed comments.